Although many people feel themselves to be familiar with Grey Walter's ideas, and with the design principles of his tortoises, most of the published sources are lacking in detail. This paper gathers together images and written material from a variety of published and unpublished sources to set both the man and his work in a richer context than has been possible for many decades. Grey Walter emerges as a fascinating and far-seeing figure whose work has not dated, perhaps because it was explicitly based on similar principles to those used today in biologically inspired robotics.